Combines for harvesting the seeds of standing agricultural crops commonly include a conventional header for cutting the portions of the crop plants that include the seeds and directing the cut portions into the threshing mechanism of the combine. These headers typically extend laterally and include a knife extending along the front edge of the table of the header to cut the plants, and a rotating reel that pushes the plats into the knife and then onto the table where an auger or belt conveys the cut plant portions into the threshing mechanism.
Stripper headers are also known where a rapidly rotating drum has closely spaced fingers which engage the plant stalks of wheat and like grains and strip the seed heads from the stalks without cutting the stalks and propel the seed heads onto the table. Such a stripper header is disclosed for example in U.S. Pat. No. 5,557,912 to Voss et al. These stripper headers thus convey only the seed bearing heads into the threshing mechanism, greatly reducing the volume of material passing through the threshing mechanism and increasing the capacity of the combine.
Other crops, such as sunflowers, are subject to significant losses with conventional headers. Sunflowers have a large seed head at the top of a tall stalk and at harvest time the stalks and heads are quite fragile such that many seeds and heads fall to the ground when contacted by the reel and are lost. Headers have been modified for harvesting sunflowers such as disclosed in U.S. Pat. No. 4,255,920 to Janzen and U.S. Pat. No. 6,032,445 to Heintzman which include seed pans that attach to the front edge of the header and extend forward of the knife. The pans are spaced to form slots between the pans. The crop plants pass along the slots and are cut by the knife at the rear end of the slots. Seeds falling from the plants are caught in the pans and work their way rearward and onto the knife. The top surfaces of the pans are flat, with raised side walls to keep the seeds on the pan. The pans are configured to slope somewhat downward from front to rear so that the seeds move down the sloping surface onto the header and into the harvester.
Hemp is a crop plant grown as an agricultural crop, with the seeds being used for food and a variety of industrial uses such as oil-based paints, in creams as a moisturizing agent, cooking, and in plastics. The long fibrous stems are also valuable for a further variety of industrial uses such as in paper, textiles, clothing, biodegradable plastics, construction, body products, and bio-fuel.
The hemp plant has a slender stem, ranging in height from 4 to 10 feet or more and a diameter from ¼″ to ¾″. Seeds are located along about the top third of the stalk and the stalk heights very considerably in the same field so that in order to harvest all the seeds the header must be operated low enough to cut off the top third of the shorter stalks.
Because it grows very tall compared other commonly grown agricultural crops, harvesting with conventional combines is often problematic. In tall varieties large quantities of plant material are put through the combine. Hemp straw contains very tough fibers that tend to wind around the moving parts and fine fibers work into bearings, causing friction that can lead to bearing breakdown and combustion. These factors cause heavy machinery wear, high maintenance costs and a great deal of time loss. Reducing the quantity of hemp stalk passing through the combine reduces contact between the moving parts and these fibers.